Soft and Fading Brakes - Adjust or Replace? (1 Viewer)

[PVCsnorkel]

My 60 sat for a couple years due to carb issues and before that the brakes were fine and stopped no issues. Now that its on the road again the brakes have been very soft and intermittently release at a stop causing me to have to push the pedal harder for the truck to stay stationary.
Before I go shot gunning parts and spending money unnecessarily, are they most likely out of adjustment or need to be bled? They don't grind and I can always come to a full stop, it just takes more pedal travel and force than it should.

 

[beatle_bayly]

So you haven't carried out a full fluid change and a thorough bleed? That would be first on my list. Fluid should be changed every two years or so anyway.

While you are underneath, have someone press the pedal while you carefully inspect the flex hoses for any swelling/bulging.

Adjust the drums (or did the US get 4-wheel discs?).

But if you are 'losing pedal' or it's sinking underfoot, you likely have a leaky slave or master cyl, which will show up through an external leak and a loss of fluid in the reservoir. Also, a leaky master cyl might leak invisibly into the booster. If the master cyl is internally leaking/bypassing, it won't result in a loss of fluid level.

 

[relaxedcruiser]

I would take the wheels/ drums off and check the brakes visiually, depending how dry it was in the enviroment where the vehicle was parked it could well be that the brake rotors are partly rusty,leaving only a fraction of the former pad/disc - shoe/drum contact area for effective braking. Also check for leaking rear wheel cylinders....that would be quite obvious though. After some years it would also be a good idea to replace the brake fluid.
Soft brakes would rule out a bad booster or not enough vacuum, if the other compents are fine.
As for the brakes I would anyway replace all the aging components regulary to keep the system as good as it can be.
I had slowly worsening quite bad / soft brakes despite all the components in good order....well not all... the pads despite only half worn had worn unevenly and the backplate was not anymore parallel with the pistons - causing them to kink - new pads fixed the issue.
Just saw that beatle_bayly posted while I was writing...hello over the ditch !

 

[PVCsnorkel]

I didn't know brake fluid had that short of a service life, I tired bleeding once but I'm not sure if I got all the air out. I have disc fronts and drum rears, to my knowledge the US cruisers were all set up that way from the factory.
I'll have to inspect the master cylinder, I was planning on pulling the drums to see what it looks like so I will check the slaves while I am in there.

 

[PVCsnorkel]

I would take the wheels/ drums off and check the brakes visiually, depending how dry it was in the enviroment where the vehicle was parked it could well be that the brake rotors are partly rusty,leaving only a fraction of the former pad/disc - shoe/drum contact area for effective braking. Also check for leaking rear wheel cylinders....that would be quite obvious though. After some years it would also be a good idea to replace the brake fluid.
Soft brakes would rule out a bad booster or not enough vacuum, if the other compents are fine.
As for the brakes I would anyway replace all the aging components regulary to keep the system as good as they can be.
I had slowly worsening quite bad / soft brakes despite all the components in good order....well not all... the pads despite only half worn had worn unevenly and the backplate was not anymore parallel with the pistons - causing them to kink - new pads fixed the issue.
Just saw that beatle_bayly posted while I was writing...hello over the ditch !

I was thinking of replacing all the pads/shoes and rotors/discs, but I wanted to make sure it wasn't a larger issues before I did. Seems master cylinder and wheel cylinders may be the culprits.

 

[g-man]

you can test the brake booster by pumping the brake pedal with the motor off. It should get a little taller with a few pushes. then turn the engine on and with vacuum boost working correct the pedal should sink. If nothing happens here your booster is shot. I drove around on a failed booster for longer than I care to admit. Weak brakes would be the result. Longer braking time/distance.

If you are not comfortable bleeding brakes because you haven't done it much or at all, I suggest getting a mity vac to pull vacuum on the bleeders while someone else pumps then holds the brake pedal. In this way you can be assured that no air is going back into the bleeder before you cut it off. The mity vac is great for testing vacuum to other components to but kind of too weak to pull a lot of brake fluid out esp from the rear brakes without some assistance on the pedal. I pulled about 20 to 25" of vacuum (pumping the hand pump on the mity vac while someone pumped up the brakes) then opened the bleeders (while someone holds pressure on the pedal) then closed them while I still had about 5" of vacuum on the gauge and had caught about 2 oz of fluid.

don't randomly replace discs, drums, pads and shoes that are not worn out. You can measure the thickness of the drums/discs with a digital caliper and check the measurement to those in the 84-90 body and chassis FSM to make sure they are in specification.

 

[CruiserTrash]

@PVCsnorkel Everyone hit it above. Start by following the FSM pedal adjustment procedure. The replace the fluid - bleed at the rear left while adding new fluid to the MC reservoir until the new fluid is coming out with no bubbles. Then rear right, then front right, then front left. New fluid at all four corners and no bubbles. It usually takes me about 3-5 rounds of this to really get it bled. Then see where you’re at.

This usually takes me 4 quarts and a helper to push the pedal is almost necessary. A second helper to keep filling the MC before it gets too low and sucks air is nice too.

 

[OSS]

The rotors are contaminated with corrosion and other crap

 

[PVCsnorkel]

I got the passenger side drum off this afternoon. It looks well used, but nothing out of the ordinary, and no signs of leaking fluid. I still have to pull the the drivers side as the drum was fighting me to come off and the bolt hole to push it off the hub no longer has threads. Just spinning the driver's side drum it sounded like it was rubbing, possibly grinding, so that may be the culprit.

I have a vacuum bleeding tool that @g-man mentioned, so after an inspection of both sides I will be flushing and re-bleeding the system. I will have to enlist the girlfriend to pump the pedal and be a helper, I will make her a cruiser head one way or another haha.

 

[beatle_bayly]

Don't forget to disconnect the lever off the rear brake load proportioning valve (if yours has one) and bleed with that all the way up, and again all the way down.

 

[relaxedcruiser]

Those drums and linings are looking good. Make sure that when pumping the pedal to replace the brake fluid - only use as much stroke on the brake pedal as you would normally use while braking. It is easy to push the pedal right to the floor if a bleed nipple is open - this can wreck the master cylinder seals as they are pushed into the part of the cylinder where they have never been before. The bore is most likely not clean there and old crap has accumulated over the years which can easily damage the seals.
Also make sure that you back up the shoes / the self adjustment before taking a drum off. This can be fiddly until you get the two little screwdrivers in the right position.

 

[relaxedcruiser]

Also - while you are there - slightly pull the dust caps of either side of the wheel cylinder - sometimes brake fluid is already present there but has not made its way out yet. If so - time to replace the cylinders.

 

[g-man]

Agreed...get a new bottle of dot3 brake fluid and top off the master cylinder reservoir after bleeding each wheel cylinder or caliper. Don't let the reservoir get too low. Looks like you have plenty of brake material on the shoes. It's also good that the push cylinders are dry and not leaking fluid. As far as re adjusting the slack adjusters goes, just put the drums back on and ratchet the hand brake several times. If it's working properly it will adjust the shoe/drum tension correctly and not over adjust. You may want to witness this by having someone pull up on the hand brake one time with the drum off, while you watch the adjusting lever contact and turn the adjusters. They can easily be moved back or shortened with the drum off. If they don't move make sure the bellcrank and lever behind the backing plate are not froze up. They often get like this if they are not used regularly.

 

[LCnAZ]

you can test the brake booster by pumping the brake pedal with the motor off. It should get a little taller with a few pushes. then turn the engine on and with vacuum boost working correct the pedal should sink. If nothing happens here your booster is shot. I drove around on a failed booster for longer than I care to admit. Weak brakes would be the result. Longer braking time/distance.

@PVCsnorkel That's the easiest test you can do, and a likely candidate IMO. Like @g-man, it took me a while to admit my problem was the brake booster. I likely replaced a master cylinder that was just fine. Also new pads and rotors were needed, but problem you describe remained. Booster. An aftermarket one solved all problems.

 

[PVCsnorkel]

Finally got the driver's side brakes off after beating on it for a while and a weather delay on the weekend. The driver's side looks just as clean and lightly used as the passenger side. I bled all 4 corners again just to be sure and the pedal definitely stiffened up. The engagement of the pedal is still super low so I'm going to try and adjust the shoes this weekend. I got to check the fronts for wear too. I'm getting closer I think though so I'll take that as a win.

 

[PVCsnorkel]

After another weekend of wrenching, I cleaned out the master cylinder and flushed all the old fluid out of the lines. The bottom of the master cylinder cup was black with dirt, so I'm guessing a lot that junk ruined my master cylinder seals. After flushing the fluid at all 4 corners, the pedal is solid when the truck is at a standstill, but as soon as I start moving it takes pushing it all the way to the floor to get any stopping power out of the brakes. The pedal sinks when I start the truck so I'm almost certain it is not the booster, though someone correct me if I'm wrong.
Is it possible to rebuild the master cylinder or am I better off with a new one?

 

[beatle_bayly]

At the age of the vehicle I'd be looking a new M/cyl, if still available at a reasonable price. But are you certain it's bled properly? Don't forget to bleed the back with the load sensing valve fully in both up and down positions (if yours has one fitted).

 

[POPO AGIE]

Master cylinders are available from several venders here on MUD. I have a new one I got from Red Line in CO for my FJ40.

 

[PVCsnorkel]

I'm fairly certain I have them bled properly. I went a couple extra times on each wheel to make sure I got all the air out. Based on how low the pedal is it's definitely more than air in the lines. When I went to flush and replace the old brake fluid there was a substantial amount of black sediment at the bottom of the reservoir, so I'm guessing that the seals in the master cylinder are all chewed up.

 

[PVCsnorkel]

What is the actual proper procedure for bleeding brakes? I think I know it but I just want to be sure I'm doing it correctly